The present invention relates to a crystal pulling unit for the production of a crystal block, which has a crucible for the meltable material which forms the crystal block and which has a recharging tube leading to the crucible to supply the meltable material in granular form.
Crystal pulling units that are generally of the aforementioned type are known for the pulling of crystal blocks of semiconductor material according to the Czochralski method. These units operate mostly continuously, in that during the pulling of the crystal block, the meltable material which ultimately forms the melt is constantly supplied in the form of a granulate. Reference is made to German Patent No. 2,821,481 as an example of the state of the art. Comparable crystal pulling units, however, are also used for semi-continuous Czochralski pulling methods. The recharging tube is made of quartz material, as is the crucible.
In the operation of such crystal pulling units, it is often determined that the recharging tube becomes clogged. This requires a shutdown of the unit, which causes relatively high costs.
It is therefore an object of the invention to design a crystal pulling unit of the type discussed above in such a way that the danger of clogging in the recharging tube is as low as possible.